Electrolytic rectifier



March 26, 1929.

G. D. BAGLEY ET AL ELECTROLYTIC RECTIFIER Filed June 28, 1924 Patented Mar. 26, 1929.

"UNITED STATES PATENT OFFjlCE.

Application filed June 28,

T his invention relates to electrolytic rectifiers, the action of which depends upon a dielectric film that is formed upon the surface of a so-ralled filming electrode when the latter and a cooperatingelectrode are immersed in a suitable clectrolyteand subjected to an electric current.

A common type. of electrolytic rectifier c0mprises a lead electrode cooperating with an electrode of filming material such as aluminum in a suitable electrolyte, such as a solution of citric acid, ammoniumcitrate or ammonium. phosphate. Lead is somewhat soluble in these and other rectifier solutions, so that there is always a soluble lead salt in the electrolyte, which stays in solution until the rectifier stands idle with no current flowing therethrough. Thereupon, the dissolved lead, even though it may be present in a very minute quantity, is precipitated as a film onto the aluminum electrode, which is strongly electropositive with respect to .lead. quently, when .the alternating current is applied, the apparatus has in effect two lead electrodes, and norectifieation takes place until electrolytic action removes the lead film from the aluminum. Y

Under such circumstances. and for example when the rectifier is connected in circuit with a storage battery to be charged from the usual current which flows while the lead film exists,

a destructive current flows through the rectifying means and damages the latter and the battery to which it is connected. This undesirable condition is most likely to occur when two rertifiers are connected in series, in charging a 100 volt li-storage-battcry from the usual 110 volt alternating current circuit, for example.

The primary object of the present invention is to avoid the foregoing objectionable performance and other deleterious action of the usual lead electrode by employing, in cooperative relation to the filming alun'iinum electrode, an electrode that is desirably electronegative toward su h filming electrode in a given electrolyte but substantially inert to the action of the electrolyte and insoluble in the electrolyte solution under all conditions, so that substantially no coating will be formed on the surface of the filming electrode that would have a deleterious effect upon the filming characteristic of the latter.

Subse- FRED T. BOWDITCH, OF ELMHURST, NEW CARBON COMPANY, INCJ," A CORPORATION ELECTROLYTIC RECTIFIER.

1924. Serial No. 723,030.

, i The accompanying drawing diagrammatically illustrates a rectifier construction and arrangement embodying the presentinvention.

As shown in the drawing, one or. more electrolytic rectifiers may beconnected inseries circuit with the ,alternating Current supply- A mains L', L and the.storagebattery B to supply direct current forchargingthelatter from I the alteri'lating currentsource. 1 For present purposes; the two. rectifiers shown are desirably identical injall essential respects. Each rectifier consists ofa suitable receptacle C for containing the electrolyte E, which may, contain a citrate radicleor consist of citric acid, a solution of ammonium citrate, ammonium phosphate, or similar substance or mixtures thereof. Cooperating electrodes. A and I are disposed in the electrolyte, in which the electrode A electropositive with respect to the electrode I. The electrode A consists ofa plate or bar offilming'materia-l such aluminum upon wl icli a dielectric ffilm zis formed during the action ofthe rectifier. The associated electrode I consist sof a solid material that is inert'toward theelectrolytefand insoluble therein under all conditions It has'been found that graphite, leadfperogtidmimangw nese peroxide andotherjsimilar conductive trodes for this purpose. ()rdinaryalngraphh tized carbon electrodes areimpracticable as the inertelectrodcs for present purposes principally because thcydeteriorate too rapidly. During-the operation oli' thc rectifier, the current supplied from the alternating current source is rectified. During such electrolytic action and also during idle periods the electrode I, that is inert toward the electrolyte, will not dissolve nor deteriorate.

An aluminum-lead rectifier may operate fairly economically under voltage conditions where a single rectifier is sullicient, because the deposit of lead upon the aluminum electrode will usually though not invariably practically correct itself. However, in any instance where the alternating voltage supplied either by a transformer or directly from the alternating current mains is so near to the battery voltage that a high protective series resistance is not used. damage as mentioned above is very likely to result. This is par tieularly true where it is advisable or necessary. especially because of the cumulative effect of high supply and battery voltages dursolid metal oxides make satisfactory elecing one-half 'Wave," to employtwoor more rectitierstoinierted'i'n series circuit with alternating current supply mains and a storage battery to be charged; tor-example, in charg- 5 inga lQOyolt storage battery from a 110 volt alternating current line. As shown, a series protective resistance D may also be employed. \Yhere two or more series-connected aluminnni-lead recti tiers a re used "after a' period of l() idleness, the ahnninum electrode of one rec- 'titierisapt' to getinto-proper workin'g eon- (lition while the iili'n ninum electrode of the otl'i'er l coated with a lead'film. The r 'fiefiwhieh' tornisitsfiltnfirst aplspareiitly"shiitsotl', by its rectifying action, the eurrent't'l'nit is e i'eetive in re-forining the film on the-"filming electrodein each of the other rectifiers. Then, the current passing through the one operatingrectifier overheats "are e'llltrti ljt esl pora ti n' thenran d even tually damaging the "reet' e and 'probably "alsothestorage"batte i'nieircuit therewith. In charging storagebatteries in series with i'nni't'teriiarin enr'rent 'so'nree'ani'l electrolytic '25"rectilying means,the i-oltage o'f'the battery whit-lb ean be chm-grid is ii'n'ii'ted'hy the breakdo\v'n voltage of or resist'anre offered by the electrolytic tihn on tlie/l'ilrning electrode. For

, "exa'n'i ilc.'tluihreafldlown voltage for the film 20 "formed on an afhiininnm electrode is about 185x141 ts and? ume n-a -tantalum elect rode is 'ithm'it "81) "volts. Tliis Him-m ion may 'he ":ivoided 'hyusing t we or niore elertrolytic reetitiers in series, the'number of re'etitiers de- :15'pendingupoirthe values o t the applied alterina'ting eurrent'anrl the terminal volta e of the charged battery. "ln' the"rectifying 'ariatifitttnfifit as illustrated in 'the'drawing, only one'h'alt \va'vei is rectified and supplied to the battery. "Here, the appliedvoltagev of the alternating; current. supply has'an' indicated yalne ofiibout lit) volts and a peak value of about 1:15 volts. terminal voltage of the charged battery is about ltlO' volts, it will he evident that. when 'no chi-rent. Hows (hiring alternate non-rectitiedhalf waves, the rectifying lihn in the cirlt it is assumed that the 'cni't sh'onld withstand-'abmrt 25 5volts; which is above the lini it oftti'e'alu'minnm electrode tihn, for instance. Accordingly, it is neces- 0 sary to conneet'two ormore rectifiers in series when the sum of the voltageof the charged battery and the peak v0 tage of the applied =alternatingfcurrent exceeds the breakdown voltage of the film on the filming electrode "o f a 'si n'gle -'r'ec'tifier.'

, As shown, the two rectifiers are connected in 'se ries wi itha 10O'yo lt' battery and a 110 volt-fiilteriratihg"currentsupply to rectify onlyaltern'at'e'half'ii zlves of the latter, and sne'h reetifiers are'et'i'etitfelyprbtectedagainst tai In re relative to one-another,because each- "(imposes "ah ii filiriing electrode of lead peroxide or the like that is inerttoward the electrolyte"?atrdWheretore' substantially no 5 leader othercdating'wi'll be forn'iedon the "tilmingeleetrotle tliatinig ht practically nul- "l ify the fi'lirr'mg' (iliar'aeteristie' of the" latter. 1 z-tifiers (if the-type disclosed may be "grouped in's'eries 'parallei and otherwise to rectify b'oth halves oft-he alternating, current wave; theel'ectrolyte niay' be of the kind disclosed inf-an"application Serial No. 721,545, file tl in the name 'otFred T. Bowditclron J une'Ql, 1924; and eiecuted on-Jun'e 17,1924;

and other-"changes may be' made in "the disclosure without departing from the spirit of this invention.

-\Ve cl'airn i 1. An"eleetrolytiereetifier comprising an 30 ele'rl-tro'lyte con titinin'g zi "'dimt'r i'a'didle, "and electrodes therein, one of said electrodes com prising aluminum"and"the other electrode comprising a conductive solid'rn'etal 'ox'ide. *2. In an eleetrolyticrectitier,the'eonibination' of ti'neleetrolyt'e estimatin a eitraite' rad 'irle and cooperating eleetrmles therein, on e fot said electrodescomprising aluminunniuul the other electrode eonaprising'lead peroxide.

Tn t'es'tiin'iony whereof, \veatfix our signa- "tn res.

GLEN D. BAGIJEY. FRED 'l BOWDITCH. 

